I was reading the Mac OS X Lion upgrade page, and it said "make sure" all over the place. It struck me as odd. Where does the term "make sure" come from? What are you making to be sure? Yourself? Shouldn't the expression be, more verbose, but more accurately, "make yourself sure", or something similar?

Anecdotically: In Spanish the latin word survives ("asegurar"), it's used in both senses ("make sure/safe some thing" and "be -someone- certain"). But the construction "make sure" is never used in this second sense, only in the first; for this we say "be sure" (estar seguro) or "asegurarse".
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leonbloyJul 21 '11 at 15:31

"Sure" means "certain", and is interchangeable. Although idiomatically "sure" is more often used to refer to a state of mind, it doesn't have to be.

You are both making it certain that Tab A is in Slot B and also making yourself certain that Tab A is in Slot B. Presumably if you have done the latter you have also done the former, so it isn't necessary to distinguish between them.